Melt the butter in a large pan and cook the bacon and onion until the onion starts to color. Add the rice , stir around the pan for 5 minutes and pour on the wine. Let it evaporate then start adding the boiling stock a ladle at a time, waiting for the liquid to be absorbed before stirring in more. After 15 to 20 minutes the risotto will be cooked al dente . Remove from the heat and stir in the Parmesan and freshly ground black pepper. Serve at once.